Effect of Yttrium Additions in Relation to Oxygen Content on Glass Formation in the Zr50Cu40Al10Alloy

The effect of yttrium additions on the glass formation of the Zr(50)Cu(40)Al(10)alloy with high oxygen content was investigated. Unlike other reports showing the positive effect of alloying Zr-based alloys with a few percent of rare earth elements, we examined the Y-to-oxygen ratios. As calculated, a stoichiometric amount of yttrium (2808 at ppm) is required to bind all the oxygen (4212 at ppm) to form the Y2O3. Additionally, the influence of half (1404 at ppm) and double stoichiometric (5616 at ppm) levels of yttrium, with respect to the measured oxygen content to be bound was evaluated. The Y-doped alloys were synthesized by arc melting, followed by suction casting into copper molds with conical and rod cavities. The critical diameter of the undoped alloy was below 3 mm, while stoichiometric and double stoichiometric yttrium concentrations allowed to obtain 5 and 7 mm diameter glassy samples, respectively. Microstructure observations confirmed the scavenging effect of yttrium, leading to the formation of a cubic (Ia (3) over bar space group) yttrium sesquioxide. The glass forming ability of the alloys was additionally determined based on differential thermal analysis, allowing to propose the best indicator for the studied Zr-Cu-Al alloys.